1. Field of the Invention
This invention relates generally to inflatable structures, and more particularly to inflatable evacuation slides with improved support.
2. Description of the Related Art
Prior art inflatable structures are typically constructed of several pieces of material adhesively bonded together to form tubular members impervious to air and water. Such tubular members are often found in water floatation devices such as life rafts, and inflatable evacuation slides or escape chutes for commercial aircraft. The inflatable evacuation slides and/or slide rafts provide a rapid means for evacuating passengers in the event of an emergency. The slides are typically constructed with two or more inflatable support tubes and a flexible floor that extends between the support members. The slides are normally stored uninflated in a container mounted on the interior of the aircraft door or immediately adjacent thereto. With the door closed, a girt bar is connected to brackets on the floor inside the doorway such that it is only necessary to open the door to automatically deploy the slide in the event of an emergency evacuation. When the door is opened, the girt bar causes release of the slide from the container and gravity causes the slide to unfold or unroll outside the doorway. Once outside the doorway, the support tubes are rapidly inflated through the application of gas pressure and, together with the floor, create a relatively stiff sliding surface for receiving evacuating passengers.
Although the rate of evacuee descent is dependent on many factors, it is primarily governed by the angle formed between the slide surface and the ground. The optimum rate of descent for evacuees is usually achieved when the angle between the slide surface and ground is between about 30xc2x0 and 50xc2x0. If the angle is much greater than 50xc2x0, the slide surface may be too steep, resulting in possible evacuee injury upon impact with the ground.
Since the slide surface has a fixed length and since the exit door may be at different heights when the aircraft comes to rest, in some instances, the ideal range of angles cannot be attained. In emergency situations where one or more of the aircraft landing gears are damaged and/or collapsed, the aircraft itself may be tilted or canted. Consequently, the aircraft door may be considerably higher with respect to the ground than when in the normal landing position. With the increase in height between the door and ground, the angle between the slide and ground also increases, leading to an undesirable rate of descent for evacuees. This phenomena can also occur for normal landing positions when the evacuation slide encounters terrain which varies in elevation.
In addition, double-decker aircraft with their ultra-high sill heights require longer escape slides to maintain the ideal angle between the slide surface and ground. Existing evacuation slides are limited by the amount of load that they are capable of carrying over a specific length. A longer length escape slide is more susceptible to undesirable bending and buckling than a shorter length escape slide when subjected to the same load. This is due to increased bending moment at the center of the longer length slide. Although the diameter of the inflatable support tubes can be increased to support greater loads, they are typically limited to approximately 24 inches. This factor in turn limits the amount of load that can be supported by the slide. The prior art, which uses substantially straight support tubes, is often not capable of producing the slide lengths necessary for the evacuation of passengers from upper decks of modern aircraft which is not deformed in use. Thus, the inflatable support tubes are typically limited in the amount of load that they can support.
In recognition of this problem, several proposals have been developed by the prior art to increase the load carrying capacity of the inflatable evacuation slides having substantial lengths. According to one such proposal, the inflatable structures have been cambered by positioning tension bands underneath the inflatable structure until the substantially straight support tubes are curved upwardly. In use, the curved support tubes tend to straighten under an applied load and are therefore capable of supporting more load at the center of the inflatable structure than the uncambered straight tubes which would normally buckle under the applied load. Although this technique is currently used throughout the industry, the formation of forced arch that can be created in the support tubes is limited, thereby limiting the length of the slide and the amount of load that can be safely supported by the slide. Thus, it has been a long felt and unsolved need to provide the inflatable evacuation devices of substantial lengths capable of transferring passengers from ultra-high sill heights without compromising reliability of the structures and safety of the evacuees.
According to the present invention, an inflatable evacuation device adapted for deployment from an exit opening of a structure comprises first and second inflatable elongate beams and a floor that extends between the beams. The floor is constructed of a flexible material, such that the inflatable evacuation device can be stored in a compact manner prior to inflation. An arch-shaped support portion comprising at least one curved beam connected to the inflatable slide portion such that forces generated at least near the central section of the inflatable slide portion are transferred to at least one curved beam to thereby support at least the central section.
Further according to the invention, an inflatable evacuation device adapted for deployment from an exit opening of a structure includes an inflatable slide portion and an arch-shaped support portion for supporting the inflatable slide portion. The inflatable slide portion has a support frame with a first inflatable elongate beam and a second inflatable elongate beam spaced from the first inflatable elongate beam. A floor extends between the first and second inflatable elongate beams and is constructed of a flexible material, such that the inflatable evacuation device can be stored in a compact manner prior to inflation. The arch-shaped support portion comprising first and second curved beams connected to the inflatable slide portion such that forces generated at least near the central section of the inflatable slide portion are transferred to the curved beams to thereby support at least the central section.